1. Field of the Invention
The present invention relates to a mobile robot, and particularly, to an apparatus and a method for detecting a position of a mobile robot.
2. Description of the Background Art
In general, a mobile robot, particularly, a robot cleaner is a device for automatically cleaning an area to be cleaned by sucking foreign substances such as dust or the like on a floor, while automatically moving along a wall surface of a room (e.g., living room, inner room or the like) of a private home without an operation of a user.
The robot cleaner discriminates a distance between itself and an obstacle installed in a cleaning area, such as furniture, office supplies, a wall or the like, through a distance sensor, and selectively drives a motor for driving its left wheel and a motor for driving its right wheel depending on the discriminated distance, so that the robot cleaner automatically switches its direction to clean the cleaning area. Herein, the robot cleaner performs cleaning, moving in the cleaning area through map information stored in an internal storing device.
Hereinafter, a mapping operation for generating the map information will now be described.
First, the robot cleaner moves along a side surface of an operation space (e.g., wall surface of living room in private home), to calculate a distance and a direction between itself and a charging station installed on a wall, and determines its position based on the calculated distance value and direction value, to scan the operation space. Herein, the robot cleaner detects its current position by using an encoder installed at its wheel.
The robot cleaner determines whether there is an obstacle between itself and the charging station. If there is no obstacle, the robot cleaner transmits/receives a signal to/from the charging station to scan an operation space. On the contrary, if there is an obstacle between the robot cleaner and the charging station, the robot cleaner scans another operation space first, and then, when the obstacle is eliminated, it transmits/receives a signal to/from the charging station to scan the operation space where the obstacle has eliminated.
However, in the method of detecting a position of the robot cleaner by using the encoder, since the current position of the robot cleaner is searched using the encoder installed at the wheel, an error occurs by sliding of the wheel or an idle rotation.
As another method for detecting a position of a robot cleaner in accordance with another conventional art, stickers or reflection plates with the same shapes are attached to an operation space (e.g., wall surface of living room of private home) at prescribed intervals, and the robot cleaner recognizes the sticker or the reflection plate by using a CCD camera to thereby compensate an error occurring by sliding of the wheel or an idle rotation, so that the robot cleaner recognizes a distance between itself and the charging station. However, in this method of detecting a position of the robot cleaner by using the sticker or the reflection plate, when illumination brightness of a cleaning area is changed or a subject having a shape similar to the sticker or the reflection plate is recognized, a distance error may be accumulated.
In addition, when illumination brightness is higher or lower than a threshold, a CCD (charge-coupled device) camera cannot recognize the sticker or the reflection plate, and thus the robot cleaner cannot check its position. In addition, since the CCD cameral has to be attached to the robot cleaner, fabrication cost of the robot cleaner is increased.
Techniques for a robot cleaner in accordance with conventional arts are also disposed in U.S. Pat. No. 5,440,216 and U.S. Pat. No. 5,646,494.